Council officials were worried it would see minicabs cutting in and out of traffic to overtake buses at stops.

They warned pedestrians would be in the firing line if cabs were allowed to roar in and out of bus lanes.

The scheme was devised to cut congestion among 8,000 private hire vehicles in the West Midlands. In a report, the West Midlands Planning and Transportation Sub Committee said: "Because private hire vehicles cannot be hailed onstreet when empty, a journey to collect the customer before going to the destination means 'double mileage' may add to congestion."

Concerns were raised because private hire cars look the same as normal vehicles. Officials believed seeing them driving up bus lanes would lead to other drivers illegally following.

The report said: "Private hire vehicles are generally less different from ordinary cars than taxis and their use of bus lanes could confuse other drivers and lead to unintentional violations, increasing the need for enforcement."

The risks to people crossing from faster cars in bus lanes and the potential for smashes with taxis overtaking buses were highlighted.

"For pedestrians crossing a road between slow moving or stationary traffic, a faster moving vehicle in an adjoining lane can create an additional road safety hazard," the report said. "Allowing private hire vehicles to use bus lanes is likely to create situation where it tries to overtake a bus at a bus stop buy cutting back into the general traffic lane."

Meanwhile, a consultation into Birmingham's first ever car-sharing lane will not start for several months, delaying its launch.

The American-style 'carpool lane' had been due to start by the end of the year on the Heartlands Spine Road.

For that to happen the consultation period - asking businesses, lobby groups and residents for their opinions - had to start shortly after the New Year.

But although a £50,000 consultation plan has been drawn up, transport cabinet member on Birmingham City Council Len Gregory has decided to wait until after the local elections in May before starting the process.

The council believes that if the initial 12-month trial period is a success, then the scheme could be rolled out around the city.

Recent research in the National Travel Survey revealed 85 per cent of vehicles on commuter journeys had just one person in them.